Compressor construction



N 1969 T. w. RUNDELL ETAL COMPRES SOR CONSTRUCTION A L 2 L 0 0 T w a mym Vfii v MM M m a a J 4 M a 6 a M 4 ma 0 a a w M M m w J J R 4 0 m F 4V. w m, a 3 m w w m. m

ATTORNEYS Sheet 5 5 Sheets- F'IG. l2

CONSTRUCTION T. W. RUNDELL ETAL COMPRESSOR ,a 0 Rd 2 Nov. 4, 1969 lNVENTORS 4 4 0001?! IV. ewwzzz ffffifl/f 0. fi/V04ZA ATTORNEYS UnitedStates Patent 3,476,308 COMPRESSOR CONSTRUCTION Theodore W. Rundell andFreddie D. Randall, Tecumseh, Mich., assignors to Tecumseh ProductsCompany, Tecumseh, Mich., a corporation of Michigan Filed Oct. 18, 1967,Ser. No. 676,107 Int. Cl. F04b 35/04, 29/00 US. Cl. 230-58 10 ClaimsABSTRACT OF THE DISCLOSURE An object of the present invention is toprovide an improved compressor construction, preferably of the hermetictype, in which as many parts as possible may be economically massproduced by stamping and/or drawing equipment, and which eliminates theneed for the usual reed-type inlet valve in the compressor pump.

Other obiects, features and advantages of the present invention willbecome apparent from the following detailed description taken inconjunction with the accompanying drawings wherein:

FIG. 1 is a vertical center section through a hermetic motor-compressorunit constructed in accordance with the present invention.

FIG. 2 is a top plan view of the unit of FIG. 1 with a portion brokenaway and taken in horizontal center section through the pump of theunit.

FIG. 3 is a fragmentary view of the stationary piston and outlet valveof the compressor pump taken in section as in FIG. 1 but on an enlargedscale.

FIG. 4 is a plan view of the outlet valve shown by itself.

FIGS. 58 inclusive are fragmentary center sectional views of the scotchyoke and pump structure of the compressor illustrating in sequence acycle of operation thereof.

FIG. 9 is a diagrammatic view illustrating the cycle of operation of thescotch yoke-inlet valve mechanism of the unit.

FIG. 10 is a vertical center sectional view illustrating a modifiedmotor-compressor unit also constructed in accordance with the presentinvention.

FIG. 11 is a horizontal sectional view taken on the line 1111 of FIG.10.

FIG. 12 is a fragmentary vertical sectional view taken on the line 1212of FIG. 11.

FIG. 13 is a horizontal sectional view on the line 1313 of FIG. 10.

Referring in more detail to the accompanying drawings, FIGS. 1 and 2illustrate a motor-compressor unit constructed in accordance with thepresent invention in which the majority of parts are adapted to befabricated from sheet metal stock by high-volume production equipment,such as stamping and metal drawing presses, to provide a lightweight,small capacity hermetic compressor at a relatively low cost. Thehermetically sealed casing of unit 20 comprises a cylindrical tube 22closed at each of its opposite ends by top and bottom covers 24 and 26respectively. Bottom cover 26 has an axially circular extending rim 28welded to the bottom of tube 22, and a 3,476,308 Patented Nov. 4, 1969domed center portion 30 disposed with its convex surface facingdownwardly. Top cover 24 likewise has an axially extending rim 32inserted with a close fit within the upper end of tube 22 and securedthereto by welding, and a domed central portion 34 disposed with itsconvex surface facing upwardly. Cover 24 also has a conventionalelectrical connector 36 with leads 38 extending in sealed relationthrough the cover. The exterior terminals of leads 38 are protected by asmall cover 40 removably retained on cover 24 by a spring clip 42 (FIGS.1 and 2) having a circular bite portion 44 which resiliently expandsinto a groove 46 provided in rim 32. By squeezing together the ends 48and 50 of clip 42 bite 44 may be contracted to remove clip 42 from cover24 and thereby free cover 40. Cover 40 may also house suitable thermaloverload protection devices of known construction.

Unit 20 includes a conventional electric motor 52 with stator windings54 mounted on an annular core 56 which in turn is suitably fixed to theinner wall of tube 22. A rotor 58 of motor 52 is mounted on a crankshaft60 for rotation therewith, shaft 60 in turn being journalled Within atubular bushing 62 which is stationarily mounted concentric with core 56and tube 22. Shaft 60 has a thrust bearing surface 63 formed as part ofthe underface of a crank throw 64 and counterweight 66 which are fixedto the upper end of crankshaft 60, surface 63 riding on the upper endsurface 68 of bushing 62. Bushing 62 in turn is stationarily supportedby a sheet metal spider frame 70 (FIGS. 1 and 2) having a central hub 72in which bushing 62 is received and welded, and three radially outwardlyextending arms 74, 76 and 78 each having an upturned end 80 secured asby welding to the inner wall of tube 22 at 120 intervals.

The scotch yoke mechanism of unit 20 includes a. cylindrical crank pin82 fixed on crank throw 64 eccentrically of crankshaft 60 so as torevolve around the axis of shaft 60 as shaft 60 rotates. Pin 82 isrotatably received in a crossbore 84 of a cylindrical slider 86 whichslides axially in the throughbore 88 of a cylindrical crosshead 90.Crosshead 90 has a pair of diametrically opposed, axially extendingslots 92 and 94 in its upper and lower sides respectively. Lower slot 94receives pin 82 therethrough and permits lateral travel of the pinaxially of crosshead '90 as seen in FIGS. 58, whereas upper slot 92provides a vent hole for oil discharged from the upper end of an oilpassage 96 which extends axially through pin 82 and shaft 60 to acentrifugal impeller tube 98 fixed to the lower end of shaft 60.

Crosshead 90 is fixed at one side thereof to a cuplike cylinder 100which constitutes the moving part of the compressor pump of unit 20. Asbest seen in FIG. 1, cylinder 100 has an end Wall 102 with a transverseconcavity 104 which receives the side of crosshead 90, cylinder 100being welded to crosshead 90 at this juncture so to be oriented with itsaxis perpendicular to the axes of crosshead 90 and crankshaft 60. Thecylindrical skirt 106 of cylinder 100 has a close sliding fit on thecylindrical skirt 10 7 of a stationary cup-like piston 108 whichconstitutes the stationary part of the compressor pump. Piston 108 has atransverse end wall 110 with a transverse groove 112 (FIG. 3) adapted tonest with the transverse convexity of wall 102 to provide essentiallyzero clearance at the end of the compression stroke of the pump whencylinder 100 is fully telescoped onto piston 108 as shown in FIGS. 1, 2and 5. Piston 108 is inserted through a circular opening 114 in the sidewall of tube 22 and welded to the rim of this opening. The outer end ofpiston 108 is closed by a plug 116 having an outlet tube 118 mountedtherein for communication with a muflier chamber 120 formed by thehollow interior of piston 108.

As best seen in FIGS. 6, 7 and 8 the space between the end walls 102 and110 of the cylinder and piston forms a variable volume pump chamber 122which is expanded and contracted by reciprocation of cylinder 100 onpiston 108. The inlet pasage to chamber 122 comprises a portion 124which extends through wall 102 adjacent skirt 106 and which registerswith a port 126 which extends through the adjacent side of crosshead 90.The inlet passage is alternately positively opened and closed insynchronism with reciprocation of cylinder 100 by slider 86 as itreciprocates in crosshead 90. As best seen in the sequence of FIGS. 6, 7and 8 one end wall 128 of the slider moves past port 126 so that theside wall of the slider completely covers port 126 just as cylinder 100reaches bottom dead center position (FIG. 7). Port 126 remains coveredand closed by slider 86 as cylinder 100 moves toward piston 108 on itscompression stroke (i.e., the discharge stroke of the pump) and untilshortly after the cylinder has bottomed on the piston at the end of thecompression stroke. As shown in the diagrammatic illustration of FIG. 9,slider 86 preferably is designed to open the inlet passage for 170 ofcrankshaft rotation and to close the inlet passage for 180 of crankshaftrotation, the uncovering and covering tolerances being accommodated bythe angular increments taken from the suction half of the pump cycle.When port 126 is uncovered by slider 86, communication is establishedbetween chamber 122 and the interior of the compressor casing via theadjacent open end of bore 88 and slots 92 and 94 in crosshead 90.

The outlet passage from pump chamber 122 comprises a port 130 extendingcentrally through end wall 110 of piston 108 to chamber 120. As bestseen in FIGS. 3 and 4, port 130 is controlled by an outlet check valve132 which comprises a thin one-piece stamping of spring steel having aflexible reed valve portion 134 adapted to seat in closed position on arim 138 formed by machining an annular groove 140 in the inner surfaceof wall 110 around port 130. Reed 134 is formed by blanking out akeyhole-shaped slot 135 (FIG. 4) from the flat bottom 144 of valvemember 132, leaving a connecting stem or hinge 142 so that reed 134 canflex between the closed and open positions thereof indicated in solidand broken lines respectively in FIG. 3. Valve member 132 also includesa pair of spring fingers 146 and 148 integrally joined to the oppositeends of bottom 144 and each having an outwardly crimped V-shaped detentportion 150 biased by the resilience of the finger so as to snapoutwardly into engagement with an annular V-shaped groove 152 (FIG. 3)in the inner wall 154 of piston 108 upon member 132 being slideablyinserted endwise through the open end of the piston to thereby securelybut removably retain valve member 132 in operative position (FIG. 3).

In operation, motor-compressor unit 20 is energized from a conventionalpower source through electrical connections (not shown) from connector36 to rotatably drive crankshaft 60 and this rotational motion isconverted by the scotch yoke mechanism into reciprocating motion ofcylinder 100 on stationary piston 108 so as to alternately expandchamber 122 to its maximum volume (FIG. 7) and contract it to almostzero volume (FIG. 5). During the suction stroke of the pump (FIGS. 5, 6and 7) the pressure differential created between chambers 120 and 122maintains reed 134 closed, while the pump inlet passage 124, 126 isopened by the spool valve action of slider 86 in crosshead 90. Thiscauses refrigerant gas to be drawn into chamber 122 from the interiorspace defined by tube 22 and covers 24 and 26 of the compressor casing.The interior space of the casing in turn communicates via suitableconnections (not shown) with the low side of the refrigeration or othersystem with which it is to be used. As cylinder 100 travels toward topdead center on its compression stroke (FIGS. 7, 8 and 5), the inletpassage is closed by slider 86, and, when the pressure of the compressedgas in pump chamber 122 exceeds that of the gas in muffler chamber 120and discharge tube 119, reed 134 opens and the compressed gas isexpelled from chamber 122 into chamber 120.

From the foregoing description, it will now be apparent that amotor-compressor unit constructed in accordance with the presentinvention lends itself to high volume low unit cost mass productionfabrication equipment and techniques. Except for motor 52 and crankshaft60, the majority of components are simple in configuration and may bestamped and/ or drawn from sheet metal stock. By having the cylinder 100arranged externally of the piston and serving as the moving part of thecompressor pump, the intake valve of the pump may be formed by thescotch yoke crosshead and slider parts, thereby eliminating one of thetwo leaf valves hitherto required.

Referring to FIGS. 10-13 inclusive, a second embodiment 200 of amotor-compressor unit of the invention is illustrated which is similarin most respects to unit 20, corresponding parts being given likereference numerals with a prime suflix. Unit 200 differs from units 20primarily in the supporting frame for motor 52 and crankshaft 60. Thus,in place of the three-legged spider 70, a cup-like frame member 202 isprovided for supporting stator 54' of motor 52' in fixed position incasing 22' and for supporting the crankshaft bushing 62' adjacent theupper end of crankshaft 60. Frame 202 has a cylindrical rim 204 whichhas a close fit against the inner wall of tube 22' and is weldedthereto. The side wall of frame 202 is generally conically shaped so asto taper inwardly and upwardly from rim 204 up to the top end wall 206of the frame. Four openings 208 are struck out at intervals around theside wall of frame 202 (FIG. 13), and four tabs 210 are bent down fromthe material taken from the side wall in forming these openings so as toextend in wardly at right angles to tube 22 to provide hangers to whichstator 54 is secured by fasteners 212.

The central portion of top wall 206 is depressed downwardly to form afrusto-conical wall 214 and a radial flange 216 the inner margin ofwhich defines a central opening through whichbushing 62' is inserted sothat a flange 63 thereof rests on and is fixed to flange 216.

The supporting framework for the motor and crankshaft of unit 200 alsoincludes a U-shaped strut 218 (FIGS. 10, 11 and 12) with a pair of arms220 and 222 bent up one from each of the opposite ends of a straightcentral portion 224 which extends horizontally and diametrically acrossthe lower end of casing 22. Each arm 220 and 222 is secured by afastener 212 to the underside of stator 54. As best shown in FIGS. 10and 11, the lower end of crankshaft 60' extends through a bushing 226which serves as an outboard bearing for the crankshaft spaced remotefrom the inboard bearing 62. Bushing 226 is formed integrally from thecentral portion 224 of the strut by a suitable piercing and drawingoperation.

The compressor pump of unit 200 differs from that of unit 20 in thatoutboard end of the stationary piston 108' is completely closed by aplug 230 (FIG. 10), the discharge tube' 118 being connected through theskirt of piston 108' and extending therefrom internally of the casing toan auxiliary muffler 232 which in turn is connected to an outlet opening236 in the side wall of casing tube 22.

Unit 200, like unit 20, thus has a majority of its components fabricatedfrom stamped and/or drawn sheet metal parts for economy of manufacture,and the com pressor pump thereof requires only one reed valve 132.

It is to be understood that the above described motor compressor unitsof the invention may be disposed for operation with the axis of rotationof the crankshaft of the unit orientated horizontally rather thanvertically as illustrated by way of example herein. The onlymodification required for horizontal operation is the substitution of asuitable oil pump for the previously described pick-up tube 98, and forthis purpose, well-known positive displacement type gear rotor or rotaryvane oil pumps or the like may be used in conjunction with a suitabledip tube for conducting oil from the oil sump to the pump inlet, as inthe manner indicated in United States Patents 1,967,035; 2,185,473and/or 2,283,024.

We claim:

1. In a motor-compressor unit, the combination comprising a casing, asupport frame connected to said casing, a motor mounted in said casing,a crankshaft supported by said frame and rotatably driven by said motor,a compressor pump disposed in said casing including a piston connectedin a fixed relation to said support frame, a cylinder externallyslidably received on said piston and defining with said piston a pumpchamber, drive means operably connecting said crankshaft with saidcylinder for reciprocating said cylinder on said piston in response torotation of said crankshaft and means forming intake and dischargepassages and valves for said pump chamber, said drive means comprising ascotch yoke mechanism including a crank pin eccentrically mounted onsaid cranckshaft, a slider carried on said crank pin and a crossheadslidably connected with said slider and connected in fixed relation tosaid cylinder, said crosshead having a surface along which said slidertravels, said intake passage means comprising a passage extendingthrough said cylinder and said crosshead between said pump chamber andsaid surface of said crosshead, said intake valve means comprising saidslider alternately closing and opening said intake passage duringreciprocation of said slider on said crosshead in response to rotationof said crankshaft.

2. The combination set forth in claim 1 wherein said discharge valvemeans comprises a discharge passage connecting said pump chamber withthe interior of said piston and a thin metallic generally U-shaped valvemember having a flat central portion containing a reed valve and furtherhaving a pair of spring arms with detent portions, said piston havingmeans in engagement with said detent portions to thereby removablyretain said valve member in operative position in said piston with saidreed valve thereof acting as a discharge check valve controlling saiddischarge passage.

3. In a motor-compressor unit, the combination comprising a casing, asupport frame connected to said casing, a motor mounted in said casing,a crankshaft supported by said frame and rotatably driven by said motor,a compressor pump disposed in said casing including a piston connectedin a fixed relation to said support frame, a cylinder externallyslidably received on said piston and defining with said piston a pumpchamber, drive means operably connecting said crankshaft with saidcylinder for reciprocating said cylinder on said piston in response torotation of said crankshaft and means forming intake and dischargepassages and valves for said pump chamber, said crankshaft beingjoumalled in a bushing adjacent one end of said crankshaft, and whereinsaid frame comprises a sheet metal frame disposed transversely of saidcasing and having a central hub portion receiving said bushingtherethrough, said frame being fixedly secured to said bushing andextending radially outwardly from said hub portion to fixed connectionswith said casing.

4. The combination set forth in claim 3 wherein said frame comprises agenerally flat central portion surrounding said hub portion and aplurality of angularly spaced arms connected at their inner ends to saidcentral portion and each having a mounting portion bent at right anglesto the outer end of the arm and Welded to said casing.

5. The combination set forth in claim 3 wherein said frame comprises agenerally cup-like member having a circular rim portion secured to saidcasing, a side wall of generally frusto-conical configuration and an endwall joined to said side wall, said hub portion comprising said end wallreceiving said bushing therethrough and providing the support thereforto form an inboard bearing for said crankshaft, and further including anoutboard bearing for said crankshaft comprising a generally U-shapedstrut having a central portion extending diametrically of saidcrankshaft and having a hub portion journalling said crankshaft near theend thereof remote from said one end, said strut having a pair of armsone at each opposite end thereof fixedly connected to said cup-likemember.

6. The combination set forth in claim 5 wherein said cup-shaped framemember has a plurality of circumferentially spaced openings in said sidewall thereof and a tab bent inwardly in each of said openings, andwherein said motor has an annular stator secured to said tabs of saidframe member.

7. The combination set forth in claim 6 wherein said crankshaftisoriented with its axis upright and said hub portion of said end wall ofsaid cup-like frame member has a downwardly depressed portion in thecenter thereof whereby said inboard bearing is supported at an elevationbelow the uppermost portion of said end wall so that oil collecting onsaid end wall drains toward said inboard bearing.

8. The combination set forth in claim 3 wherein said casing comprises acylindrical tube with a circular end plate inserted at each of theopposite ends thereof and hermetically closing said opposite ends.

9.In a motor-compressor unit, the combination comprising a casing, 21support frame connected to said casing, a motor mounted in said casing,a crankshaft supported by said frame and rotatably driven by said motor,a compressor pump disposed in said casing including a piston connectedin a fixed relation to said support frame, a cylinder externallyslidably received on said piston and defining with said piston a pumpchamber, drive means operably connecting said crankshaft with saidcylinder for reciprocating said cylinder on said piston in response torotation of said crankshaft and means forming intake and dischargepassages and valves for said pump chamber, said piston comprising acup-shaped member closed at one end by an integral end wall and havingits other end secured in an opening of said casing, said cylinder alsocomprising a cup-shaped member closed at one end by an integral end walland receiving said piston with a sliding seal fit through the other openend of said cylinder member, said discharge passage extending throughsaid integral end wall at said one end of said piston to the interior ofsaid piston.

10. The combination set forth in claim 9 wherein said piston is closedat said other end thereof by a plug member and said outlet valve isdisposed within said piston adjacent said end wall thereof so that theinterior of said piston forms a muffler chamber adjacent said dischargevalve means.

References Cited UNITED STATES PATENTS 1,445,252 2/1923 Weiss 2301742,435,108 1/1948 Touborg 23058 2,628,765 2/ 1953 Anderson 23058 ROBERTM. WALKER, Primary Examiner US. Cl. X.R. 230174

